The invention relates to a vehicle power supply system comprising a battery, a start/generator and a plurality of power consuming devices.
The production of electrical energy for a motor vehicle power supply system is usually effected with a three-phase generator which is connected with a voltage regulator. The voltage regulator regulates the generator output voltage to the value required for the voltage supply of the vehicle power system. Such a motor vehicle power supply system is known e.g. from DE-PS 33 13 398. Flywheel generators with asynchronous machines or permanently excited synchronous machines, which also serve as starters when starting and are operated with 12 volts, are known as generators. However, because of the low vehicle power supply voltage of approximately 12 volts and the low generator output voltage of approximately 12 volts, the designing of the machine is quite problematic, since large winding cross-sections are required as a result of the high electric current. In addition, high losses occur because of the high currents, and large and accordingly expensive semiconductor components are simultaneously required in the inverters for rectification of the alternating voltage produced in the generator and, when star for converting the direct current from the battery into an alternating current.